| Message ID | 20240206-ad7944-mainline-v1-2-bf115fa9474f@baylibre.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | iio: adc: ad7944: new driver | expand |
Hi David, The driver It's in pretty good shape... Just some comments from me On Tue, 2024-02-06 at 11:26 -0600, David Lechner wrote: > This adds a driver for the Analog Devices Inc. AD7944, AD7985, and > AD7986 ADCs. These are a family of pin-compatible ADCs that can sample > at rates up to 2.5 MSPS. > > The initial driver adds support for sampling at lower rates using the > usual IIO triggered buffer and can handle all 3 possible reference > voltage configurations. > > Signed-off-by: David Lechner <dlechner@baylibre.com> > --- > MAINTAINERS | 1 + > drivers/iio/adc/Kconfig | 10 ++ > drivers/iio/adc/Makefile | 1 + > drivers/iio/adc/ad7944.c | 397 > +++++++++++++++++++++++++++++++++++++++++++++++ > 4 files changed, 409 insertions(+) > > diff --git a/MAINTAINERS b/MAINTAINERS > index 4f1e658e1e0d..83d8367595f1 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -458,6 +458,7 @@ R: David Lechner <dlechner@baylibre.com> > S: Supported > W: https://ez.analog.com/linux-software-drivers > F: Documentation/devicetree/bindings/iio/adc/adi,ad7944.yaml > +F: drivers/iio/adc/ad7944.c > > ADAFRUIT MINI I2C GAMEPAD > M: Anshul Dalal <anshulusr@gmail.com> > diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig > index 59ae1d17b50d..93fbe6f8e306 100644 > --- a/drivers/iio/adc/Kconfig > +++ b/drivers/iio/adc/Kconfig > @@ -280,6 +280,16 @@ config AD7923 > To compile this driver as a module, choose M here: the > module will be called ad7923. > > +config AD7944 > + tristate "Analog Devices AD7944 and similar ADCs driver" > + depends on SPI > + help > + Say yes here to build support for Analog Devices > + AD7944, AD7985, AD7986 ADCs. > + > + To compile this driver as a module, choose M here: the > + module will be called ad7944 > + > config AD7949 > tristate "Analog Devices AD7949 and similar ADCs driver" > depends on SPI > diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile > index 5a26ab6f1109..52d803b92cd7 100644 > --- a/drivers/iio/adc/Makefile > +++ b/drivers/iio/adc/Makefile > @@ -29,6 +29,7 @@ obj-$(CONFIG_AD7780) += ad7780.o > obj-$(CONFIG_AD7791) += ad7791.o > obj-$(CONFIG_AD7793) += ad7793.o > obj-$(CONFIG_AD7887) += ad7887.o > +obj-$(CONFIG_AD7944) += ad7944.o > obj-$(CONFIG_AD7949) += ad7949.o > obj-$(CONFIG_AD799X) += ad799x.o > obj-$(CONFIG_AD9467) += ad9467.o > diff --git a/drivers/iio/adc/ad7944.c b/drivers/iio/adc/ad7944.c > new file mode 100644 > index 000000000000..67b525fb8e59 > --- /dev/null > +++ b/drivers/iio/adc/ad7944.c > @@ -0,0 +1,397 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Analog Devices AD7944/85/86 PulSAR ADC family driver. > + * > + * Copyright 2024 Analog Devices, Inc. > + * Copyright 2024 Baylibre, SAS > + */ > + > +#include <linux/bitfield.h> > +#include <linux/bitops.h> > +#include <linux/delay.h> > +#include <linux/device.h> > +#include <linux/err.h> > +#include <linux/gpio/consumer.h> > +#include <linux/module.h> > +#include <linux/property.h> > +#include <linux/regulator/consumer.h> > +#include <linux/spi/spi.h> > + > +#include <linux/iio/iio.h> > +#include <linux/iio/sysfs.h> > +#include <linux/iio/trigger_consumer.h> > +#include <linux/iio/triggered_buffer.h> > + > +#define AD7944_INTERNAL_REF_MV 4096 > + > +struct ad7944_timing_spec { > + /* Normal mode minimum CNV pulse width in nanoseconds. */ > + unsigned int cnv_ns; > + /* TURBO mode minimum CNV pulse width in nanoseconds. */ > + unsigned int turbo_cnv_ns; > +}; > + > ... > +} > + > +static int ad7944_single_conversion(struct ad7944_adc *adc, > + const struct iio_chan_spec *chan, > + int *val) > +{ > + int ret; > + > + ret = ad7944_4_wire_mode_conversion(adc, chan); > + if (ret) > + return ret; > + > + if (chan->scan_type.storagebits > 16) > + *val = adc->sample.raw.u32; > + else > + *val = adc->sample.raw.u16; > + Will this work both in big vs little endian archs? I don't think so but maybe I'm missing something. At a first glance, it seems we get big endian from spi so shouldn't we have __be16 and __be32? > + if (chan->scan_type.sign == 's') > + *val = sign_extend32(*val, chan->scan_type.realbits - 1); > + > + return IIO_VAL_INT; > +} > + > +static int ad7944_read_raw(struct iio_dev *indio_dev, > + const struct iio_chan_spec *chan, > + int *val, int *val2, long info) > +{ > + struct ad7944_adc *adc = iio_priv(indio_dev); > + int ret; > + > + switch (info) { > + case IIO_CHAN_INFO_RAW: > + ret = iio_device_claim_direct_mode(indio_dev); > + if (ret) > + return ret; > + I'm not totally sure but I think Jonathan already merged his series for the cleanup stuff for the claim direct mode. Maybe take a look and use it? Not a big win in here but I guess we could still reduce some LOC. > + ret = ad7944_single_conversion(adc, chan, val); > + iio_device_release_direct_mode(indio_dev); > + return ret; > + > + case IIO_CHAN_INFO_SCALE: > + switch (chan->type) { > + case IIO_VOLTAGE: > + *val = adc->ref_mv; > + *val2 = chan->scan_type.realbits; > + > + return IIO_VAL_FRACTIONAL_LOG2; > + default: > + return -EINVAL; > + } > + > + default: > + return -EINVAL; > + } > +} > + > +static const struct iio_info ad7944_iio_info = { > + .read_raw = &ad7944_read_raw, > +}; > + > +static irqreturn_t ad7944_trigger_handler(int irq, void *p) > +{ > + struct iio_poll_func *pf = p; > + struct iio_dev *indio_dev = pf->indio_dev; > + struct ad7944_adc *adc = iio_priv(indio_dev); > + int ret; > + > + ret = ad7944_4_wire_mode_conversion(adc, &indio_dev->channels[0]); > + if (ret) > + goto out; > + > + iio_push_to_buffers_with_timestamp(indio_dev, &adc->sample.raw, > + indio_dev->scan_timestamp); > + > +out: > + iio_trigger_notify_done(indio_dev->trig); > + > + return IRQ_HANDLED; > +} > + > +static const char * const ad7944_power_supplies[] = { > + "avdd", "dvdd", "bvdd", "vio" > +}; > + > +static void ad7944_ref_disable(void *ref) > +{ > + regulator_disable(ref); > +} > + > +static int ad7944_probe(struct spi_device *spi) > +{ > + const struct ad7944_chip_info *chip_info; > + struct iio_dev *indio_dev; > + struct ad7944_adc *adc; > + struct regulator *ref; > + const char *str_val; > + int ret; > + > + /* adi,spi-mode property defaults to "4-wire" if not present */ > + if (device_property_read_string(&spi->dev, "adi,spi-mode", &str_val) > < 0) > + str_val = "4-wire"; > + > + if (strcmp(str_val, "4-wire")) > + return dev_err_probe(&spi->dev, -EINVAL, > + "only \"4-wire\" mode is currently > supported\n"); Did you looked at spi core? I guess the chain mode is not available but IIRC spi already has spi-3wire. So maybe you could just have a boolean property for the chain mode and check both that and 3wire? > + > + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc)); > + if (!indio_dev) > + return -ENOMEM; > + > + adc = iio_priv(indio_dev); > + adc->spi = spi; > + > + chip_info = spi_get_device_match_data(spi); > + if (!chip_info) > + return dev_err_probe(&spi->dev, -EINVAL, "no chip info\n"); > + > + adc->t = chip_info->t; > + > + /* > + * Some chips use unusual word sizes, so check now instead of waiting > + * for the first xfer. > + */ > + if (!spi_is_bpw_supported(spi, chip_info- > >channels[0].scan_type.realbits)) > + return dev_err_probe(&spi->dev, -EINVAL, > + "SPI host does not support %d bits per > word\n", > + chip_info->channels[0].scan_type.realbits); > + > + ret = devm_regulator_bulk_get_enable(&spi->dev, > + > ARRAY_SIZE(ad7944_power_supplies), > + ad7944_power_supplies); > + if (ret) > + return dev_err_probe(&spi->dev, ret, > + "failed to get and enable supplies\n"); > + > + /* adi,reference property defaults to "internal" if not present */ > + if (device_property_read_string(&spi->dev, "adi,reference", &str_val) > < 0) > + str_val = "internal"; > + > + /* sort out what is being used for the reference voltage */ > + if (strcmp(str_val, "internal") == 0) { Maybe you can make the code neater with match_string() and some enum... - Nuno Sá
On Wed, Feb 7, 2024 at 4:07 AM Nuno Sá <noname.nuno@gmail.com> wrote: > > Hi David, > > The driver It's in pretty good shape... Just some comments from me > > On Tue, 2024-02-06 at 11:26 -0600, David Lechner wrote: > > This adds a driver for the Analog Devices Inc. AD7944, AD7985, and > > AD7986 ADCs. These are a family of pin-compatible ADCs that can sample > > at rates up to 2.5 MSPS. > > > > The initial driver adds support for sampling at lower rates using the > > usual IIO triggered buffer and can handle all 3 possible reference > > voltage configurations. > > > > Signed-off-by: David Lechner <dlechner@baylibre.com> > > --- > > MAINTAINERS | 1 + > > drivers/iio/adc/Kconfig | 10 ++ > > drivers/iio/adc/Makefile | 1 + > > drivers/iio/adc/ad7944.c | 397 > > +++++++++++++++++++++++++++++++++++++++++++++++ > > 4 files changed, 409 insertions(+) > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > index 4f1e658e1e0d..83d8367595f1 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -458,6 +458,7 @@ R: David Lechner <dlechner@baylibre.com> > > S: Supported > > W: https://ez.analog.com/linux-software-drivers > > F: Documentation/devicetree/bindings/iio/adc/adi,ad7944.yaml > > +F: drivers/iio/adc/ad7944.c > > > > ADAFRUIT MINI I2C GAMEPAD > > M: Anshul Dalal <anshulusr@gmail.com> > > diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig > > index 59ae1d17b50d..93fbe6f8e306 100644 > > --- a/drivers/iio/adc/Kconfig > > +++ b/drivers/iio/adc/Kconfig > > @@ -280,6 +280,16 @@ config AD7923 > > To compile this driver as a module, choose M here: the > > module will be called ad7923. > > > > +config AD7944 > > + tristate "Analog Devices AD7944 and similar ADCs driver" > > + depends on SPI > > + help > > + Say yes here to build support for Analog Devices > > + AD7944, AD7985, AD7986 ADCs. > > + > > + To compile this driver as a module, choose M here: the > > + module will be called ad7944 > > + > > config AD7949 > > tristate "Analog Devices AD7949 and similar ADCs driver" > > depends on SPI > > diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile > > index 5a26ab6f1109..52d803b92cd7 100644 > > --- a/drivers/iio/adc/Makefile > > +++ b/drivers/iio/adc/Makefile > > @@ -29,6 +29,7 @@ obj-$(CONFIG_AD7780) += ad7780.o > > obj-$(CONFIG_AD7791) += ad7791.o > > obj-$(CONFIG_AD7793) += ad7793.o > > obj-$(CONFIG_AD7887) += ad7887.o > > +obj-$(CONFIG_AD7944) += ad7944.o > > obj-$(CONFIG_AD7949) += ad7949.o > > obj-$(CONFIG_AD799X) += ad799x.o > > obj-$(CONFIG_AD9467) += ad9467.o > > diff --git a/drivers/iio/adc/ad7944.c b/drivers/iio/adc/ad7944.c > > new file mode 100644 > > index 000000000000..67b525fb8e59 > > --- /dev/null > > +++ b/drivers/iio/adc/ad7944.c > > @@ -0,0 +1,397 @@ > > +// SPDX-License-Identifier: GPL-2.0-only > > +/* > > + * Analog Devices AD7944/85/86 PulSAR ADC family driver. > > + * > > + * Copyright 2024 Analog Devices, Inc. > > + * Copyright 2024 Baylibre, SAS > > + */ > > + > > +#include <linux/bitfield.h> > > +#include <linux/bitops.h> > > +#include <linux/delay.h> > > +#include <linux/device.h> > > +#include <linux/err.h> > > +#include <linux/gpio/consumer.h> > > +#include <linux/module.h> > > +#include <linux/property.h> > > +#include <linux/regulator/consumer.h> > > +#include <linux/spi/spi.h> > > + > > +#include <linux/iio/iio.h> > > +#include <linux/iio/sysfs.h> > > +#include <linux/iio/trigger_consumer.h> > > +#include <linux/iio/triggered_buffer.h> > > + > > +#define AD7944_INTERNAL_REF_MV 4096 > > + > > +struct ad7944_timing_spec { > > + /* Normal mode minimum CNV pulse width in nanoseconds. */ > > + unsigned int cnv_ns; > > + /* TURBO mode minimum CNV pulse width in nanoseconds. */ > > + unsigned int turbo_cnv_ns; > > +}; > > + > > > > ... > > > +} > > + > > +static int ad7944_single_conversion(struct ad7944_adc *adc, > > + const struct iio_chan_spec *chan, > > + int *val) > > +{ > > + int ret; > > + > > + ret = ad7944_4_wire_mode_conversion(adc, chan); > > + if (ret) > > + return ret; > > + > > + if (chan->scan_type.storagebits > 16) > > + *val = adc->sample.raw.u32; > > + else > > + *val = adc->sample.raw.u16; > > + > > Will this work both in big vs little endian archs? I don't think so but maybe > I'm missing something. At a first glance, it seems we get big endian from spi so > shouldn't we have __be16 and __be32? Yes, in Linux SPI words are always CPU-endian. It is the drivers that use 8-bit transfers to read 16 bits that need to handle big-endian swapping. But here we are using 14/16/18 bit transfers. > > > + if (chan->scan_type.sign == 's') > > + *val = sign_extend32(*val, chan->scan_type.realbits - 1); > > + > > + return IIO_VAL_INT; > > +} > > + > > +static int ad7944_read_raw(struct iio_dev *indio_dev, > > + const struct iio_chan_spec *chan, > > + int *val, int *val2, long info) > > +{ > > + struct ad7944_adc *adc = iio_priv(indio_dev); > > + int ret; > > + > > + switch (info) { > > + case IIO_CHAN_INFO_RAW: > > + ret = iio_device_claim_direct_mode(indio_dev); > > + if (ret) > > + return ret; > > + > > I'm not totally sure but I think Jonathan already merged his series for the > cleanup stuff for the claim direct mode. Maybe take a look and use it? Not a big > win in here but I guess we could still reduce some LOC. Yes, if it is merged already, happy to make use of it here. > > > + ret = ad7944_single_conversion(adc, chan, val); > > + iio_device_release_direct_mode(indio_dev); > > + return ret; > > + > > + case IIO_CHAN_INFO_SCALE: > > + switch (chan->type) { > > + case IIO_VOLTAGE: > > + *val = adc->ref_mv; > > + *val2 = chan->scan_type.realbits; > > + > > + return IIO_VAL_FRACTIONAL_LOG2; > > + default: > > + return -EINVAL; > > + } > > + > > + default: > > + return -EINVAL; > > + } > > +} > > + > > +static const struct iio_info ad7944_iio_info = { > > + .read_raw = &ad7944_read_raw, > > +}; > > + > > +static irqreturn_t ad7944_trigger_handler(int irq, void *p) > > +{ > > + struct iio_poll_func *pf = p; > > + struct iio_dev *indio_dev = pf->indio_dev; > > + struct ad7944_adc *adc = iio_priv(indio_dev); > > + int ret; > > + > > + ret = ad7944_4_wire_mode_conversion(adc, &indio_dev->channels[0]); > > + if (ret) > > + goto out; > > + > > + iio_push_to_buffers_with_timestamp(indio_dev, &adc->sample.raw, > > + indio_dev->scan_timestamp); > > + > > +out: > > + iio_trigger_notify_done(indio_dev->trig); > > + > > + return IRQ_HANDLED; > > +} > > + > > +static const char * const ad7944_power_supplies[] = { > > + "avdd", "dvdd", "bvdd", "vio" > > +}; > > + > > +static void ad7944_ref_disable(void *ref) > > +{ > > + regulator_disable(ref); > > +} > > + > > +static int ad7944_probe(struct spi_device *spi) > > +{ > > + const struct ad7944_chip_info *chip_info; > > + struct iio_dev *indio_dev; > > + struct ad7944_adc *adc; > > + struct regulator *ref; > > + const char *str_val; > > + int ret; > > + > > + /* adi,spi-mode property defaults to "4-wire" if not present */ > > + if (device_property_read_string(&spi->dev, "adi,spi-mode", &str_val) > > < 0) > > + str_val = "4-wire"; > > + > > + if (strcmp(str_val, "4-wire")) > > + return dev_err_probe(&spi->dev, -EINVAL, > > + "only \"4-wire\" mode is currently > > supported\n"); > > Did you looked at spi core? I guess the chain mode is not available but IIRC spi > already has spi-3wire. So maybe you could just have a boolean property for the > chain mode and check both that and 3wire? I used the term "3-wire" because that is what the datasheet calls it, but it is not the same as what the SPI core calls SPI_3WIRE. The former is described in the DT bindings patch in this series and the latter means that SDI and SDO are on the same pin, which is not the case here. > > > + > > + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc)); > > + if (!indio_dev) > > + return -ENOMEM; > > + > > + adc = iio_priv(indio_dev); > > + adc->spi = spi; > > + > > + chip_info = spi_get_device_match_data(spi); > > + if (!chip_info) > > + return dev_err_probe(&spi->dev, -EINVAL, "no chip info\n"); > > + > > + adc->t = chip_info->t; > > + > > + /* > > + * Some chips use unusual word sizes, so check now instead of waiting > > + * for the first xfer. > > + */ > > + if (!spi_is_bpw_supported(spi, chip_info- > > >channels[0].scan_type.realbits)) > > + return dev_err_probe(&spi->dev, -EINVAL, > > + "SPI host does not support %d bits per > > word\n", > > + chip_info->channels[0].scan_type.realbits); > > + > > + ret = devm_regulator_bulk_get_enable(&spi->dev, > > + > > ARRAY_SIZE(ad7944_power_supplies), > > + ad7944_power_supplies); > > + if (ret) > > + return dev_err_probe(&spi->dev, ret, > > + "failed to get and enable supplies\n"); > > + > > + /* adi,reference property defaults to "internal" if not present */ > > + if (device_property_read_string(&spi->dev, "adi,reference", &str_val) > > < 0) > > + str_val = "internal"; > > + > > + /* sort out what is being used for the reference voltage */ > > + if (strcmp(str_val, "internal") == 0) { > > Maybe you can make the code neater with match_string() and some enum... I did not know about this function. Sounds useful. > > - Nuno Sá >
On Wed, 2024-02-07 at 08:19 -0600, David Lechner wrote: > On Wed, Feb 7, 2024 at 4:07 AM Nuno Sá <noname.nuno@gmail.com> wrote: > > > > Hi David, > > > > The driver It's in pretty good shape... Just some comments from me > > > > On Tue, 2024-02-06 at 11:26 -0600, David Lechner wrote: > > > This adds a driver for the Analog Devices Inc. AD7944, AD7985, and > > > AD7986 ADCs. These are a family of pin-compatible ADCs that can sample > > > at rates up to 2.5 MSPS. > > > > > > The initial driver adds support for sampling at lower rates using the > > > usual IIO triggered buffer and can handle all 3 possible reference > > > voltage configurations. > > > > > > Signed-off-by: David Lechner <dlechner@baylibre.com> > > > --- > > > MAINTAINERS | 1 + > > > drivers/iio/adc/Kconfig | 10 ++ > > > drivers/iio/adc/Makefile | 1 + > > > drivers/iio/adc/ad7944.c | 397 > > > +++++++++++++++++++++++++++++++++++++++++++++++ > > > 4 files changed, 409 insertions(+) > > > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > > index 4f1e658e1e0d..83d8367595f1 100644 > > > --- a/MAINTAINERS > > > +++ b/MAINTAINERS > > > @@ -458,6 +458,7 @@ R: David Lechner <dlechner@baylibre.com> > > > S: Supported > > > W: https://ez.analog.com/linux-software-drivers > > > F: Documentation/devicetree/bindings/iio/adc/adi,ad7944.yaml > > > +F: drivers/iio/adc/ad7944.c > > > > > > ADAFRUIT MINI I2C GAMEPAD > > > M: Anshul Dalal <anshulusr@gmail.com> > > > diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig > > > index 59ae1d17b50d..93fbe6f8e306 100644 > > > --- a/drivers/iio/adc/Kconfig > > > +++ b/drivers/iio/adc/Kconfig > > > @@ -280,6 +280,16 @@ config AD7923 > > > To compile this driver as a module, choose M here: the > > > module will be called ad7923. > > > > > > +config AD7944 > > > + tristate "Analog Devices AD7944 and similar ADCs driver" > > > + depends on SPI > > > + help > > > + Say yes here to build support for Analog Devices > > > + AD7944, AD7985, AD7986 ADCs. > > > + > > > + To compile this driver as a module, choose M here: the > > > + module will be called ad7944 > > > + > > > config AD7949 > > > tristate "Analog Devices AD7949 and similar ADCs driver" > > > depends on SPI > > > diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile > > > index 5a26ab6f1109..52d803b92cd7 100644 > > > --- a/drivers/iio/adc/Makefile > > > +++ b/drivers/iio/adc/Makefile > > > @@ -29,6 +29,7 @@ obj-$(CONFIG_AD7780) += ad7780.o > > > obj-$(CONFIG_AD7791) += ad7791.o > > > obj-$(CONFIG_AD7793) += ad7793.o > > > obj-$(CONFIG_AD7887) += ad7887.o > > > +obj-$(CONFIG_AD7944) += ad7944.o > > > obj-$(CONFIG_AD7949) += ad7949.o > > > obj-$(CONFIG_AD799X) += ad799x.o > > > obj-$(CONFIG_AD9467) += ad9467.o > > > diff --git a/drivers/iio/adc/ad7944.c b/drivers/iio/adc/ad7944.c > > > new file mode 100644 > > > index 000000000000..67b525fb8e59 > > > --- /dev/null > > > +++ b/drivers/iio/adc/ad7944.c > > > @@ -0,0 +1,397 @@ > > > +// SPDX-License-Identifier: GPL-2.0-only > > > +/* > > > + * Analog Devices AD7944/85/86 PulSAR ADC family driver. > > > + * > > > + * Copyright 2024 Analog Devices, Inc. > > > + * Copyright 2024 Baylibre, SAS > > > + */ > > > + > > > +#include <linux/bitfield.h> > > > +#include <linux/bitops.h> > > > +#include <linux/delay.h> > > > +#include <linux/device.h> > > > +#include <linux/err.h> > > > +#include <linux/gpio/consumer.h> > > > +#include <linux/module.h> > > > +#include <linux/property.h> > > > +#include <linux/regulator/consumer.h> > > > +#include <linux/spi/spi.h> > > > + > > > +#include <linux/iio/iio.h> > > > +#include <linux/iio/sysfs.h> > > > +#include <linux/iio/trigger_consumer.h> > > > +#include <linux/iio/triggered_buffer.h> > > > + > > > +#define AD7944_INTERNAL_REF_MV 4096 > > > + > > > +struct ad7944_timing_spec { > > > + /* Normal mode minimum CNV pulse width in nanoseconds. */ > > > + unsigned int cnv_ns; > > > + /* TURBO mode minimum CNV pulse width in nanoseconds. */ > > > + unsigned int turbo_cnv_ns; > > > +}; > > > + > > > > > > > ... > > > > > +} > > > + > > > +static int ad7944_single_conversion(struct ad7944_adc *adc, > > > + const struct iio_chan_spec *chan, > > > + int *val) > > > +{ > > > + int ret; > > > + > > > + ret = ad7944_4_wire_mode_conversion(adc, chan); > > > + if (ret) > > > + return ret; > > > + > > > + if (chan->scan_type.storagebits > 16) > > > + *val = adc->sample.raw.u32; > > > + else > > > + *val = adc->sample.raw.u16; > > > + > > > > Will this work both in big vs little endian archs? I don't think so but > > maybe > > I'm missing something. At a first glance, it seems we get big endian from > > spi so > > shouldn't we have __be16 and __be32? > > Yes, in Linux SPI words are always CPU-endian. It is the drivers that > use 8-bit transfers to read 16 bits that need to handle big-endian > swapping. But here we are using 14/16/18 bit transfers. > Right... > > > > > + if (chan->scan_type.sign == 's') > > > + *val = sign_extend32(*val, chan->scan_type.realbits - 1); > > > + > > > + return IIO_VAL_INT; > > > +} > > > + > > > +static int ad7944_read_raw(struct iio_dev *indio_dev, > > > + const struct iio_chan_spec *chan, > > > + int *val, int *val2, long info) > > > +{ > > > + struct ad7944_adc *adc = iio_priv(indio_dev); > > > + int ret; > > > + > > > + switch (info) { > > > + case IIO_CHAN_INFO_RAW: > > > + ret = iio_device_claim_direct_mode(indio_dev); > > > + if (ret) > > > + return ret; > > > + > > > > I'm not totally sure but I think Jonathan already merged his series for the > > cleanup stuff for the claim direct mode. Maybe take a look and use it? Not a > > big > > win in here but I guess we could still reduce some LOC. > > Yes, if it is merged already, happy to make use of it here. > > > > > > + ret = ad7944_single_conversion(adc, chan, val); > > > + iio_device_release_direct_mode(indio_dev); > > > + return ret; > > > + > > > + case IIO_CHAN_INFO_SCALE: > > > + switch (chan->type) { > > > + case IIO_VOLTAGE: > > > + *val = adc->ref_mv; > > > + *val2 = chan->scan_type.realbits; > > > + > > > + return IIO_VAL_FRACTIONAL_LOG2; > > > + default: > > > + return -EINVAL; > > > + } > > > + > > > + default: > > > + return -EINVAL; > > > + } > > > +} > > > + > > > +static const struct iio_info ad7944_iio_info = { > > > + .read_raw = &ad7944_read_raw, > > > +}; > > > + > > > +static irqreturn_t ad7944_trigger_handler(int irq, void *p) > > > +{ > > > + struct iio_poll_func *pf = p; > > > + struct iio_dev *indio_dev = pf->indio_dev; > > > + struct ad7944_adc *adc = iio_priv(indio_dev); > > > + int ret; > > > + > > > + ret = ad7944_4_wire_mode_conversion(adc, &indio_dev->channels[0]); > > > + if (ret) > > > + goto out; > > > + > > > + iio_push_to_buffers_with_timestamp(indio_dev, &adc->sample.raw, > > > + indio_dev->scan_timestamp); > > > + > > > +out: > > > + iio_trigger_notify_done(indio_dev->trig); > > > + > > > + return IRQ_HANDLED; > > > +} > > > + > > > +static const char * const ad7944_power_supplies[] = { > > > + "avdd", "dvdd", "bvdd", "vio" > > > +}; > > > + > > > +static void ad7944_ref_disable(void *ref) > > > +{ > > > + regulator_disable(ref); > > > +} > > > + > > > +static int ad7944_probe(struct spi_device *spi) > > > +{ > > > + const struct ad7944_chip_info *chip_info; > > > + struct iio_dev *indio_dev; > > > + struct ad7944_adc *adc; > > > + struct regulator *ref; > > > + const char *str_val; > > > + int ret; > > > + > > > + /* adi,spi-mode property defaults to "4-wire" if not present */ > > > + if (device_property_read_string(&spi->dev, "adi,spi-mode", &str_val) > > > < 0) > > > + str_val = "4-wire"; > > > + > > > + if (strcmp(str_val, "4-wire")) > > > + return dev_err_probe(&spi->dev, -EINVAL, > > > + "only \"4-wire\" mode is currently > > > supported\n"); > > > > Did you looked at spi core? I guess the chain mode is not available but IIRC > > spi > > already has spi-3wire. So maybe you could just have a boolean property for > > the > > chain mode and check both that and 3wire? > > I used the term "3-wire" because that is what the datasheet calls it, > but it is not the same as what the SPI core calls SPI_3WIRE. The > former is described in the DT bindings patch in this series and the > latter means that SDI and SDO are on the same pin, which is not the > case here. > Oh, I see... I could have looked at the bindings. - Nuno Sá >
> > > > > > > + if (chan->scan_type.sign == 's') > > > > + *val = sign_extend32(*val, chan->scan_type.realbits - 1); > > > > + > > > > + return IIO_VAL_INT; > > > > +} > > > > + > > > > +static int ad7944_read_raw(struct iio_dev *indio_dev, > > > > + const struct iio_chan_spec *chan, > > > > + int *val, int *val2, long info) > > > > +{ > > > > + struct ad7944_adc *adc = iio_priv(indio_dev); > > > > + int ret; > > > > + > > > > + switch (info) { > > > > + case IIO_CHAN_INFO_RAW: > > > > + ret = iio_device_claim_direct_mode(indio_dev); > > > > + if (ret) > > > > + return ret; > > > > + > > > > > > I'm not totally sure but I think Jonathan already merged his series for the > > > cleanup stuff for the claim direct mode. Maybe take a look and use it? Not a > > > big > > > win in here but I guess we could still reduce some LOC. > > > > Yes, if it is merged already, happy to make use of it here. It is in my tree, but I'd rather maintain some separation between patch sets (incase I need to pull it out again for some reason). Given the saving here is minor, we can just follow up with a patch making the conversion after both are in place. > > > > > > > > > + ret = ad7944_single_conversion(adc, chan, val); > > > > + iio_device_release_direct_mode(indio_dev);
On Tue, 6 Feb 2024 11:26:00 -0600 David Lechner <dlechner@baylibre.com> wrote: > This adds a driver for the Analog Devices Inc. AD7944, AD7985, and > AD7986 ADCs. These are a family of pin-compatible ADCs that can sample > at rates up to 2.5 MSPS. > > The initial driver adds support for sampling at lower rates using the > usual IIO triggered buffer and can handle all 3 possible reference > voltage configurations. > > Signed-off-by: David Lechner <dlechner@baylibre.com> The one thing in here that will probably bite if this gets much use of different boards is the use of non multiple of 8 word sizes. Often we can get away with padding those with trailing clocks. Any idea if that is safe here? Jonathan
On Sat, Feb 10, 2024 at 11:47 AM Jonathan Cameron <jic23@kernel.org> wrote: > > On Tue, 6 Feb 2024 11:26:00 -0600 > David Lechner <dlechner@baylibre.com> wrote: > > > This adds a driver for the Analog Devices Inc. AD7944, AD7985, and > > AD7986 ADCs. These are a family of pin-compatible ADCs that can sample > > at rates up to 2.5 MSPS. > > > > The initial driver adds support for sampling at lower rates using the > > usual IIO triggered buffer and can handle all 3 possible reference > > voltage configurations. > > > > Signed-off-by: David Lechner <dlechner@baylibre.com> > > > The one thing in here that will probably bite if this gets much use of > different boards is the use of non multiple of 8 word sizes. > > Often we can get away with padding those with trailing clocks. > Any idea if that is safe here? We can probably get away with it on these chips. The ultimate goal here, though, is to get these chips working a max sample rate which only has a few 10s of nanoseconds of wiggle room between SPI transfers. So I would rather have a bit more play in the timing than try to support generic SPI controllers.
On Sun, 11 Feb 2024 11:03:43 -0600 David Lechner <dlechner@baylibre.com> wrote: > On Sat, Feb 10, 2024 at 11:47 AM Jonathan Cameron <jic23@kernel.org> wrote: > > > > On Tue, 6 Feb 2024 11:26:00 -0600 > > David Lechner <dlechner@baylibre.com> wrote: > > > > > This adds a driver for the Analog Devices Inc. AD7944, AD7985, and > > > AD7986 ADCs. These are a family of pin-compatible ADCs that can sample > > > at rates up to 2.5 MSPS. > > > > > > The initial driver adds support for sampling at lower rates using the > > > usual IIO triggered buffer and can handle all 3 possible reference > > > voltage configurations. > > > > > > Signed-off-by: David Lechner <dlechner@baylibre.com> > > > > > > The one thing in here that will probably bite if this gets much use of > > different boards is the use of non multiple of 8 word sizes. > > > > Often we can get away with padding those with trailing clocks. > > Any idea if that is safe here? > > We can probably get away with it on these chips. The ultimate goal > here, though, is to get these chips working a max sample rate which > only has a few 10s of nanoseconds of wiggle room between SPI > transfers. So I would rather have a bit more play in the timing than > try to support generic SPI controllers. > Would just be a case of providing a fallback. If you have a good spi controller then you get better data rats. Meh, can be added later when someone needs this. We've done that a few times before. Jonathan
diff --git a/MAINTAINERS b/MAINTAINERS index 4f1e658e1e0d..83d8367595f1 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -458,6 +458,7 @@ R: David Lechner <dlechner@baylibre.com> S: Supported W: https://ez.analog.com/linux-software-drivers F: Documentation/devicetree/bindings/iio/adc/adi,ad7944.yaml +F: drivers/iio/adc/ad7944.c ADAFRUIT MINI I2C GAMEPAD M: Anshul Dalal <anshulusr@gmail.com> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig index 59ae1d17b50d..93fbe6f8e306 100644 --- a/drivers/iio/adc/Kconfig +++ b/drivers/iio/adc/Kconfig @@ -280,6 +280,16 @@ config AD7923 To compile this driver as a module, choose M here: the module will be called ad7923. +config AD7944 + tristate "Analog Devices AD7944 and similar ADCs driver" + depends on SPI + help + Say yes here to build support for Analog Devices + AD7944, AD7985, AD7986 ADCs. + + To compile this driver as a module, choose M here: the + module will be called ad7944 + config AD7949 tristate "Analog Devices AD7949 and similar ADCs driver" depends on SPI diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile index 5a26ab6f1109..52d803b92cd7 100644 --- a/drivers/iio/adc/Makefile +++ b/drivers/iio/adc/Makefile @@ -29,6 +29,7 @@ obj-$(CONFIG_AD7780) += ad7780.o obj-$(CONFIG_AD7791) += ad7791.o obj-$(CONFIG_AD7793) += ad7793.o obj-$(CONFIG_AD7887) += ad7887.o +obj-$(CONFIG_AD7944) += ad7944.o obj-$(CONFIG_AD7949) += ad7949.o obj-$(CONFIG_AD799X) += ad799x.o obj-$(CONFIG_AD9467) += ad9467.o diff --git a/drivers/iio/adc/ad7944.c b/drivers/iio/adc/ad7944.c new file mode 100644 index 000000000000..67b525fb8e59 --- /dev/null +++ b/drivers/iio/adc/ad7944.c @@ -0,0 +1,397 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Analog Devices AD7944/85/86 PulSAR ADC family driver. + * + * Copyright 2024 Analog Devices, Inc. + * Copyright 2024 Baylibre, SAS + */ + +#include <linux/bitfield.h> +#include <linux/bitops.h> +#include <linux/delay.h> +#include <linux/device.h> +#include <linux/err.h> +#include <linux/gpio/consumer.h> +#include <linux/module.h> +#include <linux/property.h> +#include <linux/regulator/consumer.h> +#include <linux/spi/spi.h> + +#include <linux/iio/iio.h> +#include <linux/iio/sysfs.h> +#include <linux/iio/trigger_consumer.h> +#include <linux/iio/triggered_buffer.h> + +#define AD7944_INTERNAL_REF_MV 4096 + +struct ad7944_timing_spec { + /* Normal mode minimum CNV pulse width in nanoseconds. */ + unsigned int cnv_ns; + /* TURBO mode minimum CNV pulse width in nanoseconds. */ + unsigned int turbo_cnv_ns; +}; + +struct ad7944_adc { + struct spi_device *spi; + /* Chip-specific timing specifications. */ + const struct ad7944_timing_spec *t; + /* GPIO connected to CNV pin. */ + struct gpio_desc *cnv; + /* Optional GPIO to enable turbo mode. */ + struct gpio_desc *turbo; + /* Indicates TURBO is hard-wired to be always enabled. */ + bool always_turbo; + /* Reference voltage (millivolts). */ + unsigned int ref_mv; + + /* + * DMA (thus cache coherency maintenance) requires the + * transfer buffers to live in their own cache lines. + */ + struct { + union { + u16 u16; + u32 u32; + } raw; + u64 timestamp __aligned(8); + } sample __aligned(IIO_DMA_MINALIGN); +}; + +static const struct ad7944_timing_spec ad7944_timing_spec = { + .cnv_ns = 420, + .turbo_cnv_ns = 320, +}; + +static const struct ad7944_timing_spec ad7986_timing_spec = { + .cnv_ns = 500, + .turbo_cnv_ns = 400, +}; + +struct ad7944_chip_info { + const char *name; + const struct ad7944_timing_spec *t; + const struct iio_chan_spec channels[2]; +}; + +#define AD7944_DEFINE_CHIP_INFO(_name, _t, _bits, _sign) \ +static const struct ad7944_chip_info _name##_chip_info = { \ + .name = #_name, \ + .t = &_t##_timing_spec, \ + .channels = { \ + { \ + .type = IIO_VOLTAGE, \ + .indexed = 1, \ + .differential = 1, \ + .channel = 0, \ + .channel2 = 1, \ + .scan_index = 0, \ + .scan_type.sign = _sign, \ + .scan_type.realbits = _bits, \ + .scan_type.storagebits = _bits > 16 ? 32 : 16, \ + .scan_type.endianness = IIO_CPU, \ + .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) \ + | BIT(IIO_CHAN_INFO_SCALE), \ + }, \ + IIO_CHAN_SOFT_TIMESTAMP(1), \ + }, \ +} + +AD7944_DEFINE_CHIP_INFO(ad7944, ad7944, 14, 'u'); +AD7944_DEFINE_CHIP_INFO(ad7985, ad7944, 16, 'u'); +AD7944_DEFINE_CHIP_INFO(ad7986, ad7986, 18, 's'); + +/** + * ad7944_4_wire_mode_conversion - Perform a 4-wire mode conversion and acquisition + * @adc: The ADC device structure + * @chan: The channel specification + * Return: 0 on success, a negative error code on failure + * + * Upon successful return adc->sample.raw will contain the conversion result. + */ +static int ad7944_4_wire_mode_conversion(struct ad7944_adc *adc, + const struct iio_chan_spec *chan) +{ + unsigned int t_cnv_ns = adc->always_turbo ? adc->t->turbo_cnv_ns + : adc->t->cnv_ns; + struct spi_transfer xfers[] = { + { + /* + * NB: can get better performance from some SPI + * controllers if we use the same bits_per_word + * in every transfer. + */ + .bits_per_word = chan->scan_type.realbits, + /* + * CS has to be high for full conversion time to avoid + * triggering the busy indication. + */ + .cs_off = 1, + .delay = { + .value = t_cnv_ns, + .unit = SPI_DELAY_UNIT_NSECS, + }, + + }, + { + .rx_buf = &adc->sample.raw, + .len = BITS_TO_BYTES(chan->scan_type.storagebits), + .bits_per_word = chan->scan_type.realbits, + }, + }; + int ret; + + /* + * In 4-wire mode, the CNV line is held high for the entire conversion + * and acquisition process. + */ + gpiod_set_value_cansleep(adc->cnv, 1); + + ret = spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers)); + if (ret) + return ret; + + gpiod_set_value_cansleep(adc->cnv, 0); + + return 0; +} + +static int ad7944_single_conversion(struct ad7944_adc *adc, + const struct iio_chan_spec *chan, + int *val) +{ + int ret; + + ret = ad7944_4_wire_mode_conversion(adc, chan); + if (ret) + return ret; + + if (chan->scan_type.storagebits > 16) + *val = adc->sample.raw.u32; + else + *val = adc->sample.raw.u16; + + if (chan->scan_type.sign == 's') + *val = sign_extend32(*val, chan->scan_type.realbits - 1); + + return IIO_VAL_INT; +} + +static int ad7944_read_raw(struct iio_dev *indio_dev, + const struct iio_chan_spec *chan, + int *val, int *val2, long info) +{ + struct ad7944_adc *adc = iio_priv(indio_dev); + int ret; + + switch (info) { + case IIO_CHAN_INFO_RAW: + ret = iio_device_claim_direct_mode(indio_dev); + if (ret) + return ret; + + ret = ad7944_single_conversion(adc, chan, val); + iio_device_release_direct_mode(indio_dev); + return ret; + + case IIO_CHAN_INFO_SCALE: + switch (chan->type) { + case IIO_VOLTAGE: + *val = adc->ref_mv; + *val2 = chan->scan_type.realbits; + + return IIO_VAL_FRACTIONAL_LOG2; + default: + return -EINVAL; + } + + default: + return -EINVAL; + } +} + +static const struct iio_info ad7944_iio_info = { + .read_raw = &ad7944_read_raw, +}; + +static irqreturn_t ad7944_trigger_handler(int irq, void *p) +{ + struct iio_poll_func *pf = p; + struct iio_dev *indio_dev = pf->indio_dev; + struct ad7944_adc *adc = iio_priv(indio_dev); + int ret; + + ret = ad7944_4_wire_mode_conversion(adc, &indio_dev->channels[0]); + if (ret) + goto out; + + iio_push_to_buffers_with_timestamp(indio_dev, &adc->sample.raw, + indio_dev->scan_timestamp); + +out: + iio_trigger_notify_done(indio_dev->trig); + + return IRQ_HANDLED; +} + +static const char * const ad7944_power_supplies[] = { + "avdd", "dvdd", "bvdd", "vio" +}; + +static void ad7944_ref_disable(void *ref) +{ + regulator_disable(ref); +} + +static int ad7944_probe(struct spi_device *spi) +{ + const struct ad7944_chip_info *chip_info; + struct iio_dev *indio_dev; + struct ad7944_adc *adc; + struct regulator *ref; + const char *str_val; + int ret; + + /* adi,spi-mode property defaults to "4-wire" if not present */ + if (device_property_read_string(&spi->dev, "adi,spi-mode", &str_val) < 0) + str_val = "4-wire"; + + if (strcmp(str_val, "4-wire")) + return dev_err_probe(&spi->dev, -EINVAL, + "only \"4-wire\" mode is currently supported\n"); + + indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc)); + if (!indio_dev) + return -ENOMEM; + + adc = iio_priv(indio_dev); + adc->spi = spi; + + chip_info = spi_get_device_match_data(spi); + if (!chip_info) + return dev_err_probe(&spi->dev, -EINVAL, "no chip info\n"); + + adc->t = chip_info->t; + + /* + * Some chips use unusual word sizes, so check now instead of waiting + * for the first xfer. + */ + if (!spi_is_bpw_supported(spi, chip_info->channels[0].scan_type.realbits)) + return dev_err_probe(&spi->dev, -EINVAL, + "SPI host does not support %d bits per word\n", + chip_info->channels[0].scan_type.realbits); + + ret = devm_regulator_bulk_get_enable(&spi->dev, + ARRAY_SIZE(ad7944_power_supplies), + ad7944_power_supplies); + if (ret) + return dev_err_probe(&spi->dev, ret, + "failed to get and enable supplies\n"); + + /* adi,reference property defaults to "internal" if not present */ + if (device_property_read_string(&spi->dev, "adi,reference", &str_val) < 0) + str_val = "internal"; + + /* sort out what is being used for the reference voltage */ + if (strcmp(str_val, "internal") == 0) { + /* internal reference is used */ + adc->ref_mv = AD7944_INTERNAL_REF_MV; + } else if (strcmp(str_val, "internal-buffer") == 0) { + /* external 1.2V REFIN and internal buffer is used */ + ret = devm_regulator_get_enable_optional(&spi->dev, "refin"); + if (ret) + return dev_err_probe(&spi->dev, ret, + "failed to get and enable REFIN supply\n"); + + adc->ref_mv = AD7944_INTERNAL_REF_MV; + } else if (strcmp(str_val, "external") == 0) { + /* external reference is used */ + ref = devm_regulator_get_optional(&spi->dev, "ref"); + if (IS_ERR(ref)) + return dev_err_probe(&spi->dev, PTR_ERR(ref), + "failed to get REF supply\n"); + + ret = regulator_enable(ref); + if (ret) + return dev_err_probe(&spi->dev, ret, + "failed to enable REF supply\n"); + + ret = devm_add_action_or_reset(&spi->dev, + ad7944_ref_disable, ref); + if (ret) + return ret; + + ret = regulator_get_voltage(ref); + if (ret < 0) + return dev_err_probe(&spi->dev, ret, + "failed to get REF voltage\n"); + + adc->ref_mv = ret / 1000; + } else { + return dev_err_probe(&spi->dev, -EINVAL, + "invalid adi,reference property: %s\n", + str_val); + } + + adc->cnv = devm_gpiod_get(&spi->dev, "cnv", GPIOD_OUT_LOW); + if (IS_ERR(adc->cnv)) + return dev_err_probe(&spi->dev, PTR_ERR(adc->cnv), + "failed to get CNV GPIO\n"); + + adc->turbo = devm_gpiod_get_optional(&spi->dev, "turbo", GPIOD_OUT_LOW); + if (IS_ERR(adc->turbo)) + return dev_err_probe(&spi->dev, PTR_ERR(adc->turbo), + "failed to get TURBO GPIO\n"); + + if (device_property_present(&spi->dev, "adi,always-turbo")) + adc->always_turbo = true; + + if (adc->turbo && adc->always_turbo) + return dev_err_probe(&spi->dev, -EINVAL, + "cannot have both turbo-gpios and adi,always-turbo\n"); + + indio_dev->name = chip_info->name; + indio_dev->modes = INDIO_DIRECT_MODE; + indio_dev->info = &ad7944_iio_info; + indio_dev->channels = chip_info->channels; + indio_dev->num_channels = ARRAY_SIZE(chip_info->channels); + + ret = devm_iio_triggered_buffer_setup(&spi->dev, indio_dev, + iio_pollfunc_store_time, + ad7944_trigger_handler, NULL); + if (ret) + return ret; + + return devm_iio_device_register(&spi->dev, indio_dev); +} + +static const struct of_device_id ad7944_of_match[] = { + { .compatible = "adi,ad7944", .data = &ad7944_chip_info }, + { .compatible = "adi,ad7985", .data = &ad7985_chip_info }, + { .compatible = "adi,ad7986", .data = &ad7986_chip_info }, + { } +}; +MODULE_DEVICE_TABLE(of, ad7944_of_match); + +static const struct spi_device_id ad7944_spi_id[] = { + { "ad7944", (kernel_ulong_t)&ad7944_chip_info }, + { "ad7985", (kernel_ulong_t)&ad7985_chip_info }, + { "ad7986", (kernel_ulong_t)&ad7986_chip_info }, + { } + +}; +MODULE_DEVICE_TABLE(spi, ad7944_spi_id); + +static struct spi_driver ad7944_driver = { + .driver = { + .name = "ad7944", + .of_match_table = ad7944_of_match, + }, + .probe = ad7944_probe, + .id_table = ad7944_spi_id, +}; +module_spi_driver(ad7944_driver); + +MODULE_AUTHOR("David Lechner <dlechner@baylibre.com>"); +MODULE_DESCRIPTION("Analog Devices AD7944 PulSAR ADC family driver"); +MODULE_LICENSE("GPL");
This adds a driver for the Analog Devices Inc. AD7944, AD7985, and AD7986 ADCs. These are a family of pin-compatible ADCs that can sample at rates up to 2.5 MSPS. The initial driver adds support for sampling at lower rates using the usual IIO triggered buffer and can handle all 3 possible reference voltage configurations. Signed-off-by: David Lechner <dlechner@baylibre.com> --- MAINTAINERS | 1 + drivers/iio/adc/Kconfig | 10 ++ drivers/iio/adc/Makefile | 1 + drivers/iio/adc/ad7944.c | 397 +++++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 409 insertions(+)